towlower.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2021 Tobias Hienzsch
 
#ifndef TETL_CWCTYPE_TOWLOWER_HPP
#define TETL_CWCTYPE_TOWLOWER_HPP
 
#include <etl/_cwchar/wint_t.hpp>
#include <etl/_cwctype/iswupper.hpp>
 
namespace etl {
 
/// \brief Converts the given wide character to lowercase, if possible.
///
/// \details If the value of ch is neither representable as a wchar_t nor equal
/// to the value of the macro WEOF, the behavior is undefined.
///
/// https://en.cppreference.com/w/cpp/string/wide/towlower
///
/// \ingroup cwctype
[[nodiscard]] constexpr auto towlower(wint_t ch) noexcept -> wint_t
{
    if (iswupper(ch) != 0) {
        return ch + wint_t(32);
    }
    return ch;
}
} // namespace etl
 
#endif // TETL_CWCTYPE_TOWLOWER_HPP